1. Field of the Invention
The present invention relates to ink for inkjet printing.
2. Discussion of the Background
Various different inkjet recording methods have been proposed, for example, a method of utilizing electrostatic attraction to eject ink droplets (so-called electric-field control method), a method of utilizing vibration pressure of a piezoelectric element to eject ink droplets (so-called drop-on-demand method (pressure pulse method)), and a method of utilizing pressure that is generated by forming and developing air bubbles with high temperature (so-called thermal inkjet method). These methods allow extremely high-definition images to be obtained.
These inkjet recording methods typically use water-based inks using water as the main solvent and oil-based inks using organic solvent as the main solvent. Generally, images printed using a water-based ink have poor water resistance, while oil-based ink can provide images having excellent water resistance.
Thus, various inkjet inks have been developed and used.
If the pH of an inkjet ink is shifted to the acidity side, head nozzles may be eroded (corroded), thus causing non-ejection and deflection of ink. For example, in a solvent/oil-based ink, corrosive substances (e.g., acid substances) are generated due to deterioration of the ink, adverse effects are caused by water absorption and moisture absorption, and degradation of resin (e.g., degradation of vinyl chloride-vinyl acetate copolymer resin) can occur. If the pH of the inkjet ink is shifted to the acidity side due to such corrosive substances, a head nozzle member is eroded, thus causing non-ejection and deflection of ink.
Conventionally, there is a precedent that an anti-rust material such as benzotriazole is added into the ink so that it adsorbs onto the surface of the head nozzle member so as to form a protective layer for preventing the erosion of the head nozzle member. However, this does not prevent the pH of ink from being shifted to the acidity side (see, e.g., JP-A-2006-225603).
Thus, it is desired to provide an inkjet ink that is effective in preventing the nozzle member from being eroded.